The Lotus F1 chief made public his bid for the club via his twitter feed earlier this week.
A statement from the official site poured cold water over any potential takeover.
“We have received an email from Tony Fernandes regarding an offer for a share of the club which has immediately been rejected. He has announced this on Twitter and people can draw their own conclusions as to the seriousness of it from that.
“We are not looking to sell the club but, as we have always said, we would love co-investors to join us in rebuilding West Ham United, which has been our aim ever since we took charge back in January 2010.
“In the event that a serious investor came forward as was the case at Chelsea and Manchester City, we would naturally consider it for the good of the club - but this is certainly not the case in this instance.
“This kind of approach is very unhelpful when we have just made a big step forward as a club in our hope of returning to the Premier League, and it distracts from our main focus which is promotion.”